2000 Chrysler Concorde has a knocking sound when it accelerates. What can it be?

Knocking upon acceleration is one of those problems that causes a mechanic to check nearly every part of the car.

Priority - Action - Part Type - Cause
1 Inspect Distributor Cap - Loose or Cracked Distributor Cap.
2 Inspect Wireset - Worn, Damaged, Faulty, or Wireset Ends Are Not Completely Connected/Inserted.
3 Inspect Spark Plug - Fouled, Damaged, or Broken Spark Plug(s).
4 Inspect Spark Plug Gap - Incorrectly Gapped or Fouled Spark Plug(s).
5 Inspect Timing Belt - Slipped or Broken Timing Belt.
6 Inspect Timing Chain - Slipped Timing Chain.
7 Inspect Timing Set - SlipPed Timing Chain or Worn Timing Gear(s).
8 Inspect Point Gap - Incorrect Point Gap Setting.
9 Inspect Point Set - Burned, Worn or Incorrectly Set Ignition Points.
10 Inspect Ignition Coil - Faulty Ignition Coil.
12 Inspect Knock Sensor - Improperly Connected or Faulty Knock Sensor.
13 Inspect EGR Position Sensor - Worn, Damaged or Faulty EGR Position Sensor.
14 Inspect Air Pump Check Valve - Worn, Damaged or Faulty Air Pump Check Valve.
15 Inspect EGR Valve - Improperly Functioning or Faulty EGR Valve.
16 Inspect Firing Order - Spark Plug Wire(s) Not Connected in Correct Firing Order Sequence.
17 Inspect Timing Specification - Incorrect Ignition Timing.
18 Inspect Barometric Pressure Sensor - Damaged or Faulty Barometric Pressure Sensor.
19 Inspect Distributor Rotor - Loose or Cracked Distributor Cap. Worn/pitted Rotor.
20 Inspect Fuel Filter - Clogged or Dirty Fuel Filter.
21 Inspect EGR Time Delay Switch - Worn, Damaged or Faulty EGR Time Delay Switch.
22 Inspect EGR Vacuum Solenoid - Worn, Damaged or Faulty EGR Vacuum Solenoid.
23 Inspect Carburetor - Worn, Faulty, Damaged, Dirty, Improperly Functioning, or Incorrectly Adjusted Carburetor.
24 Inspect Point Dwell - Point Dwell Not Within Specified Range.
25 Inspect Compression Pressure - Low Compression.
27 Inspect Ported Vacuum Switch - Worn, Damaged or Faulty Ported Vacuum Switch.
30 Inspect Heater Control Valve - Leaking or Faulty Heater Control Valve.
31 Inspect Camshaft Gear - Worn Timing Gear(s).
32 Inspect Crankshaft Gear - Worn Timing Gear(s).
33 Inspect Main Bearing - Worn or Damaged Main Bearing.
34 Inspect Carrier Bearing - Loose, Worn or Damaged Carrier Bearing.
35 Inspect Oil (Crankcase) Type and Weight - Incorrect Grade of Motor Oil.
36 Inspect Camshaft Bearing - Worn or Damaged Camshaft Bearing.
37 Inspect Fuel Octane - Low Octane causing pre-ignition when going uphill/accelerating.

Sounds like it could either be a spun out main bearing or camshaft bearing or it could be knocking from low octane gas, depending on how loud it is. A main bearing or camshaft bearing that is spun will make an unmistakably loud cyclic noise. While, the low octane gas will cause a softer random rapid knocking sound that sounds like a babbling brook. Check for codes in the engine that might explain why there is an octane related knock, like a knock sensor not working or something like that. Good luck on finding a solution to your knocking problem.